Online apparel store ModCloth is turning to its user data to solve one of the biggest problems with buying clothes online -- ordering clothes that fit the first time.

The popular vintage-inspired retailer launched a new feature for its iPhone app Friday that surfaces products for you based on the reviews of other users who have similar measurements. Called "fit for me," the feature uses an algorithm to pull the matching data, which includes height, bra size, waist, and hips. It seems like a simple idea, but ModCloth is in the unique position of having the data to power it effectively.

Over 80 percent of the site's products have reviews and 55 percent of those reviews include user measurements, according to ModCloth. That's huge, considering how important reviews are to consumers when they are deciding on a purchase.

But ModCloth's method may be the way customers trust the most because of the site's loyal following. ModCloth fosters this by making customers feel like they are apart of the business. They can vote on which items will go on sale through the site's "be the buyer" feature and includes shoppers in the design process with "make the cut" feature. This idea extends to "Fit for me," since it relies on its users to provide the data the is needed for a good fit.

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Customers willingly post their measurements and even photos of themselves wearing the garments in order to aid their fellow shoppers in their purchase decisions. A scan of the reviews show that many people give specifics, like how true to size an item is.

"The reviews are a really powerful way for shoppers to understand not only how it looks like in detail but also how it fits," said ModCloth Product Manager Fontaine Foxworth.

The fit for me option will only pull from products that are actively on sale. On average, it will select from about 900 products and about 8,800 reviews. It's unclear if that this would scale for a larger inventory, but it works for ModCloth's niche community.

In testing, shoppers who only saw a list of recommended products with no explanation didn't trust the results, but placing people's review next to them instills confidence, Foxworth said.

ModCloth plans to expand it to its other platforms like Android and the Web eventually, but it started with iOS because that's where the bulk of its visits and revenue comes from, said Sarah Rose, ModCloth's VP of Product and Growth. When the company added the ability to write a review to its iOS app in May, the number of reviews and photos uploaded to ModCloth daily increased by 30 percent, according to the company.